The present invention primarily relates to a method for data communication, in particular for coupling bus users of an open automation systems, and a freely programmable communication processor according to the independent claims. Furthermore the present invention relates to a method for data communication, in particular for D11 configuration, and an apparatus with a flexible communication structure, in particular a programmable controller. Finally the present invention relates to a method and a device for data communication, in particular for synchronization of communicating among each other bus users of an automation system with distributed control functions over a serial data bus.
Already for a longer time in the control and automation technology field busses and Ethernet are used, in particular the extension regarding Real-Time Ethernet for data communication between individual units being involved in controlling a process. Examples for known field busses are CAN-Bus, profibus, modbus, DeviceNet or Interbus. The communication of the units is carried on the field bus/Ethernet on the basis of specified protocols. In order to comply with demands for open systems for networking, it is necessary to provide simple and low-cost systems for networking in order to make industrial appliances capable for networking. This demand is particularly important with respect to coupling drive components, such as between drive controls, power units and transmitters in NC machine tools and robots, regarding which a plurality of interpolating axles have to be operated synchronously. In times of increasing networking of most different technical systems the demand for standardized structures in the industry grows accordingly.
One example for this requirement is the field bus according to the so-called Actuator-Sensor-Interface-standard, in short ASI-standard. This field bus concept is specifically designed for making binary sensors or actuators directly bus-capable, which could not be obtained with other field bus systems up to now. An automation system consists of hardware components being connectable to said bus system, in particular motors, sensors, actuators, inter alia—that is the process environment—which by acting together with one or more superior controls constitute an automatic production process. The bus master then takes over all tasks being necessary for the processing of the bus operation. As a rule the bus master is separated from the actual control unit for controlling the hardware components.
In order to easily obtain an open and flexible operating mode of the system, wherein the hardware components may be exchanged without changing the control programs, in DE 198 50 469 A1 an automation system and a method for accessing the functionality of hardware components is disclosed, wherein as a mapping of the current functionality of hardware components these provide a system connection unit with function objects each, wherein the function objects are provided for accessing the functionality of the hardware components over the bus system. In order to implement the hardware components as “plug and play” modules it is necessary to provide a special function block directly placed in the hardware component, on which the function objects are operable giving access to the functionality of the hardware components. This special function block is implemented in the form of the system connection unit. This system connection unit is coupled to a bus system of the automation system such that for example communication data can be transmitted from a management system to the hardware component as well as from and to all further components coupled to the bus system. By the system connection unit thus it is possible to substitute or to add, etc., hardware components without changing existing structures of the automation system. Furthermore special node elements, which were required up to now between the management system and the hardware components, can be left out. For a network transition the system connection unit provides a memory for storing protocols required between both bus systems. Thus in a very simple way a network transition between ETHERNET (data transfer rate 10 Mbit/s), in particular the FAST ETHERNET (data transfer rate 100 Mbit/s—standard IEEE Std. 802.3-1998), and the profibus may be obtained. The embedding of the system connection units assigned to the hardware components in their environment may be designed such, that the function objects comprise at least one first function object for generating a minimal functionality of one hardware component, at least one second function object for interconnecting function objects and at least one third function object for listing function objects provided in the system processing unit and/or in removed system processing units and/or in removed computers. The particular function of the function objects is to enumerate, i.e. to enquire the functionality sum of the system. For example the function objects are designed as so-called DCOM-objects (Distributed Component Object Model) or as so-called OLE-objects (Object Linking and Embedding). Furthermore the system connection unit provides a runtime-system as well as a protocol-processing unit (Profibus, UDP/IP, RPC). Therefore the system connection unit represents a standard module, which has to provide protocols specified for the field bus, and which is often quite complex and therefore relatively expensive.
In order to allow a fail-safe communication of units involved in a safety-critical process, wherein at the same time the use of standard modules as bus masters is permitted, in DE 199 28 517 C2 a management system is disclosed, wherein the bus master is connected to the field bus separately from a first control unit and a signal unit, wherein the first control unit is arranged upstream of a signal unit with respect to a circulation direction of the telegram traffic, and wherein the first control unit provides means to substitute telegram data being addressed to the signal unit with fail-safe telegram data. It is then possible to connect said first control unit as a simple bus user, i.e. without a bus master functionality, to the field bus. Furthermore the control system provides a second control unit to control non-safety-critical processes, being connected to said field bus separately from said first control unit. Apart from other already known components the second control unit provides a micro controller as well as a master-protocol-chip. In the present case the master-protocol-chip provides a bus master functionality for an interbus and is named “bus master”. Such master-protocol-chips are obtainable as standard modules from different manufacturers. A communication module contained in the first control unit provides a slave-protocol-chip being connected to the field bus on the input side via a first bus interface and via a second bus interface on the output side. The protocol chip corresponds to the protocol chips contained in signal units, which connect safety-relevant devices to the field bus as bus users. In order to provide a slave-to-slave communication between bus users in a field bus with sequentially circulating telegram traffic, wherein no bus user has a bus master functionality, the protocol chip of a bus user, which intends to send data to other bus users, will be supplemented with a transmitting memory and if applicable with a receive memory. The operating principle of the circulating telegram traffic is accordingly based on the arranged in the same way slave-protocol-chip in each bus user, often named as “Serial Microprocessor Interface” (SUPI). Because of using a standard module obtainable from different manufacturers, the cost for a control system may be kept low; altogether the cost for the bus master and the signal units, which have to provide specified protocols for the field bus, are complex and relatively high.
A similar solution is disclosed in DE 299 07 909 U1 with respect to a tracking system implemented in a production system based on plug-in boards. In detail each plug-in board provides a microprocessor, a memory unit storing process data and being connected to said microprocessor, a sensor bus interface (RS 485) and a field bus interface (RS 485) both being connected to said microprocessor, a service interface (RS-232) for connection to a modem and an interface (ISA-bus interface) for connecting the microprocessor to a host computer. The integrated field-bus interface, or the sensor bus interface, each provide an ISO-interface and a field bus data processor (SPC 3), in the present example a profibus-data-processor. A machine control is optionally connected to the plug-in board via the integrated profibus interface or to sensor-electronic units via an II/O-box. The intelligent sensor-electronic-units each allow the supply of one sensor, the collection of sensor data, the pre-processing of measuring signals (signal filtering, signal amplification, etc.) and the simple signal analysis (digital filtering, collecting peak values, etc.). Therefore an intelligent sensor-electronic-unit implies being a module providing an own micro-controller, filter, amplifier, power supply and a sensor bus interface. The sensor-electronic-unit may be newly parameterized via the plug-in board before each processing. This concerns for example the amplification factors, the filtering values and the clearing of several input signals to one sum signal. By the profibus interface the monitoring may be synchronized to the processing operation. Via so-called automated setting routines the monitoring system may be easily implemented in the production appliance. The automated setting routines for example perform the speech perception on the controller and the connected to it speech switching, the recognition of the sensors on the sensor bus and the automatic configuration of the amplification and filter values. The inputs and outputs of the programmable logic controller (SPS) are assigned automatically and the time of a real time clock on the plug-in board will be automatically coordinated with the time of the host computer. The plug-in board allows to monitor for example up to four sensor channels, wherein for the sensor bus interface a data rate up to 460.8 kBaud, at the same time having a high interference immunity, may be obtained with the communication processor. Preferably the microprocessor of the plug-in board processes data in Hamming code with a Hamming distance of 4 and carries out the encoding and decoding. Between the microprocessor and the ISA-interface towards the host computer an address decoder is included carrying out the encoding and decoding of address and memory accesses in a PC in a per se known way. The power supply of the plug-in board is carried out via the ISA-interface, across which the communication to the host computer is carried out as well. Because the plug-in board has its own processor being in charge of the monitoring, the CPU of the host computer shall not be reserved for processing power. A real-time capable sensor bus protocol is defined for the communication with the sensor-electronic-units. Thus the enquiry of the measuring data as well as the controlling and parameterizing of the sensors with defined response times is made possible. The monitoring data are processed in a cycle of 10 ms and the pre-processing of sensor data allows a scan frequency below 1 ms. Thus a response time below 1 ms may be guaranteed for a collision monitoring. Beside the synchronization data also process specific axle signals can be transmitted via the field—or the profibus in a preferable way like torques, motor currents and axle speeds. The protocol allows for example the enquiry of up to eight different axles. Via the field bus the required control data can also be directly delivered out of the control core of the machine control to the microprocessor of the plug-in board. In this case no specific sensor technology is needed and the sensor bus interface on the plug-in board may be left out. Via the service interface all settings, software updates as well as process visualization may be carried out. In case said service interface is designed as a modem interface then teleservice and telediagnostic service functionalities are available via a modem. Accordingly the system becomes fully operable and parameterizable under remote control. The visualization of process data may be performed by a program on the host computer (controller, industry-PC). As the plug-in boards and the intelligent sensor-electronic-units, which have to provide protocols specified for the field bus, are complex and relatively expensive this may be deemed a disadvantage again.
Furthermore in DE 198 31 405 A1 a control system with a personal computer is disclosed, which provides for processing a control program at least one PC-processor, one program memory and one data storage and which provides a communication processor for the connection to a field bus, to which sensors and/or actuators for controlling a process may be connected. For the communication on the field bus a plug-in board is inserted in the PC, which is connected to an internal PCI-bus, which provides data-, control- and address lines. Via a PCI-bus connection and the internal bus the PC-processor communicates with the components of the plug-in board. The communication processor is arranged on the plug-in board and automatically carries out a cyclic data transfer on the field bus after a corresponding parameterization of the PC-processor and mainly consists of an ASIC. The communication processor is operable as a master on a field bus with cyclic data transfer like the PROFIBUS DP and functions as clock source when collecting process data. Further a memory is provided in which process data delivered on the field bus are stored. This memory then stores a current process map, which the PC-processor may access at any time. In order to relieve the PC-processor of the polling of incoming process data or of monitoring the field bus, a control unit is provided. The control unit may be implemented through a hardware circuit being parameterisable, but also through an expansion of the communication processor program in form of a software solution. The hardware circuit then comprises a small RAM being embedded in the address space of the PC-processor and therefore may be directly addressed by the PC-processor and a programmable logic module, which according to a corresponding parameterization stored on the RAM monitors the cyclic data transfer on the field bus and/or incoming data on the field bus. When starting the control program in the program memory the PC processor accesses the RAM and sets the corresponding bits therein, thus determining the function of the control unit as required. By this parameterization it may be determined for example in which cases the control unit has to generate an interrupt, which is transmitted via the PCI-bus connection and on the PCI-bus to the PC-processor. Thus it may be determined, in which cases the PC-processor shall be prompted by the control program to further process data received on the field bus. In case of active process control the communication processor as a master continually polls all users on the field bus, for example sensors like a flow meter or a level meter converter, actuators like supply or discharge valves in a tank, which are operated as slaves. In case the communication processor read in process data of a slave, it intends to store those in the memory cells of the memory provided for the individual process data. The logic block of the control unit reviews by the address of the write access, if an interrupt has to be generated in case of a change of the individual process data. This review can easily be carried out, because the process data of each slave are stored at fixed memory locations within the memory. If an interrupt has to be generated in case of a particular data change, a data comparator implemented within the logic block compares data put on the bus by the communication processor with previous process data, which previously have been read out of the memory by the logic block. Because the comparison of currently received data to previous process data as well as the interrupt-generation is carried out by a control unit implemented in hardware-form thus a very quick response of the control system to the change of process data is possible in a favorable way. The disadvantage again is that the communication processor and the control unit, which have to provide specified protocols for the field bus, are complex and therefore relatively expensive.
The use of (Fast)-Ethernet transfer technology is also known regarding the networking of different communication systems. For example in DE 100 47 925 A1 a method for the real-time communication between several network users within a communication system with Ethernet-physics is disclosed, wherein a master unit and one or more slave units communicate among each other by transmitted over the network telegrams, a cyclical exchange of telegrams takes place with equidistant sampling points, wherein each slave unit is synchronized to the master unit by a shared time basis and an access control for the transmit and receive mode between the network users is performed by a time slot-access method. In the automation technology the demands on the performance of communication systems are particularly high, for example regarding the coupling of driving components. The data transfer time, in the control loop taken into account as lag time, is an especially important parameter when exchanging data between transmitters, power units and a driving control. The smaller this lag time the higher a dynamic volume can be obtained by the control system. Because in the automation technology a highly accurate compliance with real-time conditions is required as well as a high data transfer safety, the standardized transmitting layer 2 (telegram frame and access method) of the (Fast)-Ethernet, which does not comply with these demands, shall be defined completely new by a new telegram frame and a new access control and with this the Ethernet-physics is used as a basis for a real-time communication between, for example, driving components. The communication between the control unit and the transmitters and the power units as well as the connection to a motion control can then be implemented. In order to obtain a cyclical data transfer with same sampling times, a shared time basis for the master and all slaves is implemented. The synchronization of the slaves to the master is carried out by specifically marked up, time wise defined telegrams of the master sent to the slaves and individually parameterized timing registers within the slaves. The user data can be transmitted on a telegram frame, which provides—beside the slave addressing and the telegram length information—the securing of the data integrity by, for example, a CRC-check sum and further security-related data ranges. An application processor may not only evaluate the data on the telegram frame, but also by a communication block, thus providing a second initiating channel. Although the applied transfer technology according to the Ethernet-standard in principle only permits point-to-point-connections, the establishment of networks can be obtained by using network nodes (so-called HUBs) as used in (Fast)-Ethernet-networks, wherein several or each network user has a switch unit to establish a network node, which serves for the transmission of the telegrams in the direction of another master unit or further slave units. Then also hierarchical networks with point-to-point-connections with Ethernet-physics connected via network nodes can be established for the realization of a real time communication within larger network topologies. This is also useful for a networking or coupling of a distributed driving system, wherein a first communication system comprises a numeric motion control as a master unit and at least one control unit as a slave unit, wherein each control unit serves as a master unit of a further communication system, which provides at least one power unit to drive a motor and an assigned transmitter system as slave units. Via Fast Ethernet-line drivers within each network user and possible network nodes the telegrams reach the particular protocol components, which process the telegram protocol and in which the time slot access method is implemented. If the protocol component is independent from a microprocessor of the slave-application (the actual power unit), particular application events may be initiated by the control-bits of the telegram frame within the slave without requiring the assigned to the slave microprocessor or corresponding software. This corresponds to a second initiating channel like it may be required for particular security-related applications (i.e. emergency stop, etc.)
In DE 100 04 425 A1 a network with a plurality of network users, for example sensors and actuators, is disclosed, which are connected among each other over the network for the data transfer. In order to obtain an improved precision of the clock synchronization, the first telegram comprises a corrected by a transmission time delay time of a first network user, and a second network user is designed such that it measures the time delay since reception of the first telegram and to correct the time received in the first telegram by the lead time and the reception time delay. If the second network user is furthermore designed such that it is able to send a second telegram for clock synchronization to a third network user, which contains a received time corrected by the lead time and the delay between reception of the first telegram and sending of the second telegram, thus an iterative re-sending of always corrected clock times from network user to network user is feasible. Furthermore start and end of the lead time of a telegram can be defined as the point of time, at which a characteristic field of a telegram with a defined spacing from the telegram beginning leaves a Media-Independent-interface of the first network user, or enters into a Media-Independent-interface of a second network user. Measuring the transmission time delay, lead-time and reception time delay not depending on the length of each telegram may be advantageously. If the network components comply with the Ethernet-, Fast-Ethernet- or Gigabit-Ethernet-specifications, the type-field of the telegram can be used advantageously as a characteristic field of the telegram. A network user, in particular a field device, can be provided with several ports, in particular four ports, for the connection to further network components. Then an interface, a so-called microprocessor-interface, can be provided for the connection of the ports with a network user internal processor bus and a control unit, a so-called switch-control, which initiates a telegram re-direction between the ports and the microprocessor-interface. This has the advantage that network users, in particular field devices, can be interconnected in a linear structure as usually done by field bus users. A separate switch, like required in a star-shaped structure, is not necessary. The integration of switch-functions within the network users has the advantage that in particular regarding Ethernet the CSMA/CD-access control can be deactivated and the network obtains a deterministic behavior. With this the range of applications of network users and the network is extended to those applications, where real-time behavior is required. A gateway for coupling network areas of different physics and with different protocols is not necessary. The communication with application-specific switch units of network users is performed by a microprocessor bus, to which a RAM, a microprocessor and a microprocessor-interface are connected. Task of the microprocessor is to process application programs and communication functions, for example the processing of TCP/IP. A further task may be the management of transmission and receptions lists of telegrams of a different priority within an external RAM. Furthermore four Ethernet-controllers are arranged in an ASIC of the communication interface. Each of those Ethernet-controller enters the data bytes of a fully received telegram into a reception list within the RAM through a multiplexer, a DMA-controller, which is also called a DMA 2-control, and the microprocessor-interface. The microprocessor accesses the reception list and evaluates the received data according to an application program. The microprocessor-interface forms the essential interface between the Ethernet-controllers and the microprocessor bus. It controls and arbitrates the write and read accesses, which are carried out through the DMA-controller or the DMA-controller on the RAM. If DMA-requests of both DMA-controllers are sent, the microprocessor-interface decides on the access rights of both DMA-channels. The microprocessor can further write parameter-registers via the microprocessor-interface, which serve for the operation of the communication interface of the network user. A device of the Ethernet-controllers, named as Transmit-Control, comprises a control unit, which performs the transmission of telegrams, repetitions, transmission abortion, etc. It forms the interface between the internal controller cycle and the transmit cycle. For storing a transmit-status-information for low-prior and high-prior telegrams a transmit-status-register is provided in this device. If a telegram has been sent fail-safe via the port, a corresponding interrupt will be generated. The Media Independent Interface (MII) integrates the MAC-sublayer of layer 2 according to the seven-layer-model, i.e. the data-link-layer. This forms an interface to a block for the physical data transfer. Further the MI comprises a transmit-function-block as well as a receive-function-block. In addition a MAC-control-block, an address filter, a statistical counter and a host-interface are integrated. Control and configuration data can be transmitted to the block via the MII and status information can be read from it.
In distributed automation systems, for example in the sphere of drive technology, specific data must be received by specific users at a particular point of time (i.e. real-time critical data) and must be processed by the recipients. According to JEC 61491, EN61491 SERCOS interface-technical abstract (http://www.sercos.de/deutsch/index deutsch.htm) a successful real-time critical data transfer of the mentioned kind can be provided in distributed automation systems. From the automation technology synchronous, clocked communication systems with equidistance-features are known as, for example, disclosed in DE 101 40 861 A1 for a system and a method for transmitting data between data networks. In detail the first data network provides first means for the data transfer in at least one first transmission cycle, wherein said first transmission cycle is divided into one first range for the transmission of real-time critical data and a second range for the transmission of non real-time critical data. The second data network provides second means for the data transfer in at least one second transmission cycle, wherein said second transmission cycle is divided into a third range for the transmission of real-time critical data and a fourth range for the transmission of non-real-time critical data. For the coupling of data networks with the same or different communication protocols, for example, Ethernet-data-networks, in particular isochrone real-time Ethernet-communication systems, with PROFIBUS-data networks or isochrone real-time Ethernet data networks with SERCOS-data networks and/or FIREWIRE-data networks or PROFIBUS-data networks and/or FIREWIRE-data networks with SERCOS-data networks, finally a coupling unit (Router) is provided for transmitting real-time critical data from the first range to the third range. The possibility to be able to transmit real-time critical data from one data network to another, is used for transmitting cycle-synchronization-telegrams from one clock source of one data network to the other data network, in order to also synchronize local relative clocks by the cycle-synchronization-telegrams in the other data network. Therefore the different data networks have own clock sources each. Because of the cycle synchronization across data networks in each data network user a relative clock can be implemented, which represents an unambiguous time across the system. Based on this basic mechanism events in both communication systems can be collected with a shared time-related understanding or time-related switch-events can be initiated in the own or the other data network. The accuracy of the relative clock corresponds at least to the accuracy of one transmission cycle. The router may then be designed as a discrete device or as an integral part of one user of one of the data networks, wherein also the routing of acyclic, demand controlled communication, for example Remote Procedure Calls (RCP), between the data networks is feasible and the corresponding communication may be carried out with proprietary and/or open protocols.
Automation components (i.e. controllers, drives) in general have an interface to a cyclically clocked communication system. One process level of the automation component (fast-cycle, for example position control in a controller, speed and torque control of a drive) is synchronized to the communication cycle, through which the communication cycle is determined. Other algorithms of the automation component running slower (slow-cycle, for example temperature control) may only communicate with other components via this communication cycle as well (for example binary switch for fans, pumps), even if a slower cycle would be sufficient. By using just one communication cycle for transferring all information across the system high demands arise with respect to the bandwidth of the transmission path. Accordingly for each process or automation level the system components use just one communication system or one communication cycle (fast-cycle) for communication, all relevant information being transmitted in the given cycle. Data, required only in a slow-cycle, can be transmitted gradedly by additional protocols to limit the bandwidth requirements. In DE 101 47 421 A1 a method is disclosed wherein a second user in a switchable data network controls one first user in a switchable data network, wherein the control loop can be closed over the switchable data network. For this purpose the communication between users of the switchable data network is provided via one or more point-to-point connections within synchronized to one another transmission cycles. For the communication of actual and ideal values, or of correcting variables over the data network the real-time-capable band of a transmission cycle is used and the communication of required for the control data telegrams is carried out within determined time windows. Further also a guide value may be transmitted over the switchable data network, which is generated by one of the users of the data network for one or several users of the data network. This could be, for example, the collection of an actual value of an axle, i.e. of a so-called master axle, of a facility. Based on this actual value the particular user generates a guide value, which serves for controlling so-called slave-axles. The functionality of such a control, for example a programmable logic controller, a motion-control system or a numerical control may also be integrated in a drive. Apart from the coupling of an input/output-station to a control unit also a relative clock may be generated within one user. The relative clock is generated by a master clock and cyclically distributed within the network thus implementing the same set of time in all users involved in the network. The time basis for the relative clock is then given by the synchronous transmission cycles and/or subdivision of transmission cycles into time slots. Based on this shared time, events may be collected with time stamps (for example edge identification of digital I/Os) or switching processes (for example switching of digital/analog outputs) may be marked with time stamps and the switching output may be processed based on this shared relative time. Within the real-time communication several communication cycles are potentially provided in order to implement different “quality of services”, like for example: 1 ms-cycle for sync connections (guide value via bus), speed target-/position target-/I/O-interface for time-sensitive axles, fast I/O-coupling or 4 ms-cycle for non-time-sensitive axles (frequency converter, simple positioning axles), application data for example: emergency-stop-control, shared shifting register (product pursuit), driving (for example modes of operation) in distributed systems, instruction of new drilling operations (for example drill depth) of automatic drilling machines or asynchronous and/or event-controlled cycle for projection-data and -events or data and routines for error handling and diagnosis.
In order to provide a method for making up a communication system for industry automation based on Ethernet having an essentially determinable communication behavior, response times in the lower ms-range and low cost regarding the communication nodes, finally in DE 100 55 066 A1 a method for multidirectional exchange of information between users (for example programmable controllers) is disclosed. Dependent on the size of the sent Ethernet-data-packet (telegram) it will be subdivided into several smaller packets (short telegrams) and at least one control information will be added to each packet, said smaller packets will be transmitted to their target in several cycles and if applicable will be put back together to the original Ethernet-data-packet by means of the control information. All telegrams, the length of which is longer than the length of the short telegrams, will be subdivided and all short telegrams have the same fixed length. Source and target of the short telegram, no matter whether subdivided or not, independent of in how many short telegrams it was subdivided, and the current number of the short telegram can be learned from the control information. For the multidirectional exchange of information between users (for example programmable controllers), wherein a user may be assigned to an industrial domain switch (IDS), which is connected to the IDS via an Ethernet-connection, the IDS are structured as a network via a connection in conformity with Ethernet and each IDS obtains a time wise determined transmission right controlled by a determined, cyclic framework. When starting the system or restarting it (Power On or Reset) the assignment of a transmission right will be negotiated between the IDS via a management function by management telegrams, regarding which the IDS recognize that those are management telegrams. The entire control logic of the IDS may be integrated into a high-integrated electronic component.
As shown by the foregoing description of the present state-of-the-art, in the automation technology various interfaces with their physical characteristics and transmission protocols are defined for the communication between individual devices and are standardized according to international specifications or become established as industry standards. These systems are generally called field bus systems, wherein also Ethernet-based technologies belong to those. The interfaces are made up in form of dedicated communication-controllers, partly with CPU as integrated circuits (communication-processor) as shown for example in DE 198 31 405 (ASIC: ASPC2), DE 299 07 909 (ASIC: SPC3), DE 199 28 517 C2 (ASIC: SUPI), DE 100 04 425 A1. As well the entire interface is often designed as an exchangeable module, comprising a connector, physical interface, dedicated communication-controller, microprocessor with memory and transfer logic to the CPU of the programmable controller, as a rule a Dual-port Memory. This module realizes exactly one specific transmission protocol and has to be specifically developed in its entirety to comply with this requirement. As a rule the communication-processor comprises only one specific communication-controller for a specific field bus system, however in the meantime circuits are available, which comprise several of these dedicated communication controllers, as it is disclosed in the U.S. patent application Ser. No. 09/780,979 for a communication-controller according to the CAN-standard and a communication-controller according to the Ethernet-standard. As a rule then specific hardware and software components are required together with some expensive components particularly adapted to communication requirements, like HUB and line drivers, Ethernet-controllers, Media Independent Interface for the connection to another network (public data network, other LAN or a host system), field bus interfaces or sensor bus-interface, in particular Serial Peripheral Interface with Master- or Slave-protocol-chips, as well as the conversion of corresponding network-access-protocols, for example CSMA/CD (Carrier Sense Multiple Access/Collision Detection), Token-Passing (binary pattern as authorization mark) or TCP/IP (Transmission Control Protocol/Internet Protocol) in for the field bus specified protocols. Almost no attention is paid to the development of such a circuit or a communication interface permitting an individual and comfortable matching of communication functions independent of a specific field bus system. As a rule the communication-controller implements only one specific field bus system for the communication of the usual SPS-function blocks, wherein for example drives are synchronized to each other via fast, deterministic and jitter-free communication connections. This is carried out by detecting a specific data or event in the communication controller, which initiates the downstream CPU by an interrupt to execute the synchronous drive functions, like measuring the position or the output of the correcting variables. This method has the disadvantage that the accuracy of the synchronization is decisively affected by the interrupt-latencies of the CPU, in particular when using operating systems, which block the interrupts for specific periods of time. Therefore in practice low-cost methods and communication interfaces are missing for an automation system operable in real-time, which ensures an individual, in particular automatically adjustable, interactive communication or allows a simple exchangeability or function blocks for an automation system operable in real-time, which also without additional hardware-function modules and without costly adaptation of interfaces establish quick and economically demanding automation solutions. In particular this is important, because the telecommunication and computer industry, in particular in the sphere of automation and drive technology, can be deemed very progressive and innovative industries, which very quickly pick up improvements and simplifications and implement those.
Object of the invention is to design a method for data communication of bus users of an open automation system such that the connection of an optional number of bus users to an individual, interactive communication may be permitted. Further objects are to provide exchangeability of parts of the apparatus or to provide an automatic and highly accurate synchronization.